Senior U.S. officials have sent several "feelers" to Iran about restoring diplomatic relations and are privately predicting direct talks will begin "over the next six months," administration sources say.

With Iran's acceptance of a cease-fire in its war with Iraq, "suddenly everyone is thinking big," in the words of one administration official.Interviewed recently on the condition of anonymity, the various sources said President Reagan is prepared to restore relations if the revolutionary regime of the Ayatollah Ruhollah Khomeini provides firm assurances for the security of a reopened U.S. Embassy, agrees to help win freedom for American hostages in Lebanon and ceases support for terrorist groups worldwide.

Officials acknowledged that some White House factions are pushing for a full resumption of relations before the November elections to boost Vice President George Bush's presidential hopes.

State Department specialists, however, called such a scenario highly unlikely and noted Iran's radical government simply may be unwilling to accept U.S. demands.

Even before Monday's formal announcement of gulf cease-fire, relations between the United States and Iran showed new signs of thawing, despite the public outcry from Tehran following the Navy's fatal downing of Iran Air Flight 655 over the Persian Gulf July 3.

Immediately following the tragedy, Reagan said the United States would offer compensation to families of the 290 victims and senior administration officials voiced hope that the "humanitarian gesture" would lead to a broadening of contacts between the two countries.

Some U.S. intelligence officials trace the sudden warming to talks at the U.S.-Soviet summit in June on a general easing of global conflicts.

One Pentagon intelligence analyst said that during the summit, American and Soviet officials certainly talked about ways to end the gulf war and agreed to support U.N.-backed peace efforts.

Other intelligence sources maintain Iran is believed eager to end its own diplomatic isolation as a means of improving its struggling economy.